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Steedeite

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Formula:
NaMn2[Si3BO9](OH)2
System:
Triclinic
Colour:
Colorless to pale pink; ...
Name:
Named in 2013 by M. M. Haring and Andrew M. McDonald in honor of Anthony Hosford Steede, dedicated mineral collector and specialist in the minerals of Mont Saint-Hilaire, Quebec, Canada.
Closely related to the sérandite-pectolite series of the pyroxenoid group and is the first mineral found to contain single loop-branched dreier silicate chains.

Classification of Steedeite

Approved 2013
Explanation of status:
A different material was originally approved as a new mineral (IMA 2010-049), but the approval was later withdrawn in October 2011 since further investigations had shown that the mineral is identical to catapleiite.

Subsequently a different mineral was submitted as IMA2013-052.
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http://www.mindat.org/min-41101.html
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Type Occurrence of Steedeite

General Appearance of Type Material:
Bundles of slightly radiating acicular crystals to 0.5 mm.
Place of Conservation of Type Material:
Type material is deposited in the collections of the Royal Ontario Museum, Queen’s Park, Toronto, Ontario, Canada, catalogue number M56489
Geological Setting of Type Material:
Late-stage mineral in sodalite syenite

Physical Properties of Steedeite

Sub-Vitreous, Silky
Diaphaneity (Transparency):
Transparent, Translucent
Colour:
Colorless to pale pink; white
Streak:
White
Tenacity:
Brittle
Cleavage:
None Observed
Fracture:
Irregular/Uneven
Density:
3.106 g/cm3 (Calculated)

Crystallography of Steedeite

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Space Group Setting:
P1
Cell Parameters:
a = 6.837(1) Å, b = 7.575(2) Å, c = 8.841(2) Å
α = 99.91(3)°, β = 102.19(3)°, γ = 102.78 (2)°
Ratio:
a:b:c = 0.903 : 1 : 1.167
Z:
4
Morphology:
Acicular crystals.
X-Ray Powder Diffraction Data:
d-spacingIntensity
8.454(100)
7.234(39)
3.331(83)
3.081(38)
2.859(52)
2.823(80)
2.477(21)
2.169(25)

Optical Data of Steedeite

Type:
Biaxial

Chemical Properties of Steedeite

Formula:
NaMn2[Si3BO9](OH)2
Essential elements:
All elements listed in formula:

Other Names for Steedeite

Name in Other Languages:

Other Information

Weak pale green to pale yellow fluorescence under medium-wave radiation
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Steedeite

Reference List:
Haring, M.M. and McDonald, A.M. (2013) Steedeite, IMA 2013-052. CNMNC Newsletter No. 17, October 2013, page 3002; Mineralogical Magazine, 77, 2997-3005.

Haring, M.M.M. & McDonald A.M. (2014): Steedeite, NaMn2[Si3BO9](OH)2: Characterization, crystal-structure determination, and origin. Canadian Mineralogist, 52, 47-60.

Internet Links for Steedeite

Localities for Steedeite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Canada
 
  • Québec
    • Montérégie
      • La Vallée-du-Richelieu RCM
        • Mont Saint-Hilaire
Haring, M.M. and McDonald, A.M. (2013) Steedeite, IMA 2013-052. CNMNC Newsletter No. 17, October 2013, page 3002; Mineralogical Magazine, 77, 2997-3005; Haring, M.M.M. & McDonald A.M. (2014): Steedeite, NaMn2[Si3BO9](OH)2: Characterization, crystal-structure determination, and origin. Canadian Mineralogist, 52, 47-60.
Mineral and/or Locality  
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